Fibrous conduit and method of manufacture



Feb. 27, 1945. 7 2,370,193

FIBROUS CONDUIT vAND METHOD OF MANUFCTURE Filed Saga. 5, 1942 2 Sheets-Shet 1 3215mm Edward/$38M;

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Patented Feb. 27, 1945 UNlTED STATES PATENT orrlcs FIBROUS CONDUIT AND METHOD OF MANUFACTURE Edward s. Reid, Charlotte, N. 0., assignor to Sonoco Products Company, a corporationof South Carolina Application September 5, 1942, Serial No. 457,427

13--Claims.

One of the most important features of my invention is the time saving and economic method and means of providing plug and socket forms at the ends of the conduit sections for'coupling purposes. By utilizing what I have termed a slip-sleeve construction, I provide plug or socket forms at the ends of the paper tubes without the necessity of any grinding, cutting, compressing or any of the conventional procedures for effecting endwise connections between conduit sections.

In accordance with my invention I form the' desired conduit by partially nesting or telescoping a fibrous tube of a certain diameter into another similar tube of just sufiiciently larger diameter to afford a sliding or slip fit. Thus the two tubes or sleeves are combined in concentric, slip-sleeve fashion.

Now to obtain the plug and socket forms or couplings at the ends of the concentric tubes, one tube is pulled out or displaced endwise from the other for a desired short distance, such as 1-3 inches. This automatically produces, at the ends of the tubes, the coupling forms, which may be termed as male and female or plug and socket. The usually necessary operations of cutting, grinding, or compressing are completely avoided and remarkable savings in labor and tools are obtained.

In practice it is usually desirable to have the plug or socket forms of uniform length on all conduit sections so that the desired neat and reliable fit or coupling is obtained at the junctions of the conduit sections laid end.to end. I ob- .tain this result by using tubes of the same length so that when telescoped they form the same length or size plug and socket at the resp ctive ends of the conduit section.

To maintain the two tubes in displaced position, whereby the coupling forms are obtained, any suitable adhesive such as for example sodium silicate, or dextrine may be employed.

, When the tubes are not subsequently treated this adhesive'may constitute the sole and permanent bonding agent. However, the tubes are usually,

subsequently, impregnated to render them water resistant so that they may be embedded in soil or concrete or may be exposed directly to the weather. The impregnating-material, if of an adhesive type, may then serve as a supplemental or principal bonding agent to hold the two tubes in the desired displaced arrangement.

For the general purposes of my invention, I have found it advantageous to use as an impregnating material, a coal'tar pitch manufactured by the Barrett Company and well known in the trade as Fibre Pitch. This material is solid at ordinary temperatures but upon heating forms a sufficiently thin fluid to penetrate the paper tubes without the use of an organic solvent or thinner. To facilitate impregnation of the tubes with this Fibre Pitch, I usually carry out the treatment in a heated, closed, vessel, which may be operated under vacuum or positive pressure. Alternating between sub and super atmospheric pressures gives good results for certain types of tubes.

Another very desirable feature of my invention is made possible from the discovery that this Fibre Pitch or equivalent material can serve, when properly handled, as the bonding agent for coupling together sections of the conduit. For thispurpose an excess of the pitch is permitted to remain on the plug and socket coupling ends, afterthe impregnating treatment. This excess coating, which is very hard at room temperature, may be softened by heat, e. g. a blow torch, and while soft the abutting ends of the conduit sections can be brought together; the plug end of one section fitting into the socket end of the next section. Then upon cooling the pitch again hardens and sets to provide a strong, rigid joint or coupling.

While -I have mentioned especially coal tar pitch, my invention contemplates the use of any and all other suitable thermoplastic or thermosetting agents including suitable natural or synthetic gums and resins. The material covering the ends of the tubes is advantageously thermoplastic so that it may be softened for coupling and uncoupling purposes.

The slip-sleeve conduit unit of my invention may be made in any desired diameter or length.

Commercially useful examples are, 10 foot lengths and diameters of 1 inch to 6 inches. The wall thickness of the conduit is made up of the combined thicknesses of the two paper tubes. Total wall thickness of /zinchto 1 inch are commonly used. The aper or fibrous tubes used in my invention may be convolutely or spirally. wound In actual installations, it is often necessary to use a shorter length section to "piece-out the final length or space.- For this purpose I have provided relatively short couplings of about one .foot or less in length. These couplings are also made by my slip-sleeve method and provide vthe desired lug or socket forms at their respective ends.

These couplings differ in one respect from the regular length conduit sections in that, the two tubes of which they are made, are not of identical length but are of appreciably difierent lengths. By varying the respective lengths of the outer and inner sleeves. or tubes, different type couplings may be obtained; for example couphngs having two plug ends, or two socket ends, or one plug and one socket end.

For purposes of connecting my type of conduit to that of some other make, which uses ground or cut plugs or sockets, I have provided a suitable adapter. This adapter also comprises two .tubes in concentric, slip-sleeve arrangement with plug or socket. ends, but has one or both ends tapered to fit the complementary part of the other make of conduit. This tapering may be effected by any of the conventional tooling operations. The lengths of the two tubes comprising the adapters may be varied as described above for the couplings, to provide desired plug and socket ends.

The constructional features of my invention are illustrated in-the accompanying drawings, in which:

Fig. 1 is a side elevational view, partly in section, of the slip-sleeve conduit unit of my invention;

Figs. 2 and 3 are side elevational views, partly in section, of my slip-sleeve couplings; and

Fig. 4 is a side elevational view, partly in sec-' tion, of a slip-sleeve adapter.

The conduit shown in Fig. 1 is comprised of an inside paper tube III, which for example may have an outside diameter of slightly less than 3% inches, and a wall thickness of /1 inch; and an outer paper tube i I, which for example, may have an inside diameter of slightly more than 3% inches and a wall thickness of inch. These tubes In and Ii are bonded together in the telescopic arrangement shown and are impregnated throughout their thickness with Fiber Pitch as indicated at Id. The two tubes being of the same length and displaced lengthwise as shown, provide a plug l3 and a socket ll, at their respective ends. These members connect with compleplug [3 will connect with any of the regular sockets 14 in my conduits and the tapered socket 15 will connect with a reversely tapered plug of some other conduit section. The outer tube ll of this adapter has a thicker wail than the reguiar tubes to provide extra strength and support particularly along the tapered and thinner wall section I! of the inner tube.

A commercially advantageous method of impregnating the fibrous conduit, couplings, and adapters of my invention to render them water resistant, is as follows: Theconduits, couplings, or adapters, previously assembled in slip-sleeve manner and bonded with adhesive, are placed in a tank or suitable chamber containing fiber pitch heated to about 260 F. to 300 F. At such temperatures the pitch is in a fluent state and is absorbed by the paper tubes, which are permitted to remain in the pitch for varying lengths of time depending upon the wall thickness of the tubes and the ultimate use of the conduit. Generally, the tubes remain in the treating chamber for a period of thirty minutes to two hours.

To facilitate the impregnation, a vacuum of about 12 inches to 13 inches may be applied to the treating chamber and maintained for a period ofabout thirty minutes. The vacuum is then brokerfand a positive pressure of about twenty pounds is then applied for a period of about 15 minutes to minutes.

At the higher temperatures the pitch is more fluid and will therefore run off of the tubes when they are removed from the treating tank, particularly from the inside surface of the tubes since it will remain hotter than the outside surface after the tubes are removed from the tank. At a temperature of about 290 F. to 300 F. the pitch will quickly run off the inner surface of the tubes and leave a slick smooth finish. This is desirable where the conduits, etc., are to be used a for electrical wires; the smooth surface facilitatmentary shaped ends ofsimilar conduit sections when installing a long line of conduit. The excess pitch indicated at ll provides means for bonding the sections together by softening with heat as described above.

The coupling in Fig. 2 comprises inner and outer paper tubes .II and l lthe same as Fig. 1 except that the overall length is much less, and the inner tube II is not of the same length as the ing' drawing of the wires or cables through the conduits. Where the conduits, etc., are to be used for waterpipe, it is advantageous to leave an excess of the pitch both on the inner and outer surfaces thereof to render the conduits, etc. water resistant. To obtain this result a lower temperature of about 260 F. to 270 F. is maintained in the impregnating tank.

In the above described operations the ends of the paper conduits will cool more rapidly, upon removal of the conduits from the impregnating tank, and will thereby cause an excess of the pitch to be deposited at these ends. This is desirable since the excess material will serve as a bonding agent, upon heating with a blow torch or the like, as previously described.

It will be apparent from the above description 1 that various modifications may be made of the the couplings in Figs. 2 and 3 may be formed.

if desired, from tubes of equal length and displaced so as to provide a plus and a socket at the outer tube II. This arrangement provides a socket II at each end. p

- In Fig. 3 the coupling arrangement is the converseofthatinmg.2,sothataplug llisprovided at each end of the coupling.

The adapter, shown inFig.4 comprises an inner tube ll thatis tapered on one end as shown at I! to form a -socket, and extends beyond the outer tube'st-the other end to form a plug IS. The

respective ends. Likewise, the outer sleeve of the adapter may be machined or tooled at the end to provide a tapered plug or socket. Also, the

inner sleeve malbe made shorter than the outersleeve and thereby provide two socket ends, one or both of which may be tapered; It also happens;

. in some projects. that it is required to usc tubing of other makes, possibly'of end-formation and dimensions differing from that oi the standard tubing ofthe present invention. To meet such.

contingency special adapter-couplings it are provided, as shown in Figs. to 9, inclusive. These adapter-couplings have, at one end, either an exact duplicate of the bell or socket portion 14 or of the pin or plug portion I3 of the standard tube of the present invention. At the other end of the adapter-couplingis either a bell or socket portion IQ, of form and dimension to receive the pin or plug portion of the different make of tubing, or else a pin or plug portion 20 is provided to fit into the bell or socket portion of the said tubing of a diilerent make.

In Fig. 5, the illustrated adapter-coupling I8 is female at both ends, i. e., it has at one end a bell or socket I4 like that of the coupling shown in Fig. 2, and at its other end an adapting bell or socket 19 to receive the counterpart pin or plug end of the joined make of tube.

In Fig. 6, the adapter-coupling I6 is malefemale, i. e., it has an adapting bell or socket [9 at one end like that of the element shown in Fig. 5, but, instead of the standard bell or socket II, it is provided with a standard pin or plug i3 at its other end. i

In Fig. '7, another male-female adaptercoupling I8 is illustrated. In this form, there is a standard bell or socket M at one end of the element and an adapting pin or plug 20 at the other end.

ill

duit, comprising two paper tubes secured together I with a thermoplastic, water resistant material,

that permeates said tubes and said adhesive and is effective in providing a strongly bonded unitary conduit construction, and said short, end, coupling elements having an excess coating thereon of said thermoplastic material which upon heating will serve as a bonding agent for joining said conduit with another similar section of conduit.

2. A prefabricated, double-walled, fibrous conduit comprising two fibrous tubes bonded to-' gether, in fixed, concentric, telescoped relationship, by an adhesive that is substantially fiuid at room temperatures and is deposited as a relatively, thin bonding film between the contiguous walls of the two tubes, said tubes being displaced for a short section of their length to provide correspondingly short plug or socket coupling In Fig. 8, the adapter-coupling shown is entirely male, i. e., it has a standard pin or plug H at one end and an adapting pin or plug 20 at its opposite end.

Preferably, the respective adapter-couplings l8, illustrated in Figs. 5 to 8, inclusive, are of the slip-sleeve construction and impregnation treatment like the tubes of the present invention. However, inasmuch as the special adapting bells or sockets l9 and pins or plugs 20 have to be 'formed'by a cutting or grinding process (or a combination of both) the wall thickness of these elements is appreciably increased to permit this' operation without weakening the structure. An example of this wall-thickening appears in Figs. 5 to 8, inclusive. Therein. the walls of both the inner and the outer of the two she-assembled tubes of the composite structure are thickened. equally, more than the thicknesses of the two tubes l0 and H composing either the standard tube sections of the present invention or those inner and outer tubes composing the standard couplings shown in Figs. 2 and 3.

Instead of producing the adapter-couplings l8 from slip-sleeve tubes of the same wall thickness. an even more practical and preferable way to construct the adapter-couplings is. to utilize an outer tube 21 of a maximum. increased wall thickness. inserting therein a tube 22 oi 'minimum wall thickness. In this way the standard bell or socket portion H is produced without any cutting or grinding operation. So, too. there is less cutting away or grinding required to produce the adapting bell or sockets l9 and th ada ting pins or plugs 20 of the adaptercouolinga. Other possible modifications will anpear to those skilled in this art. and are intended vention.

I claim: l. A- prefabricated, double-walled, fibrous conelements of equal length at the respective ends of the conduit, and said conduit being adapted for impregnation by a suitable waterproofing material.

3. A prefabricated, impregnated, fibrous conduit adapted to be used underground, comprising two fibroustubes bonded together in fixed. concentric, telescoped relationship by a normally fluid penetrative adhesive located in and upon the contiguous wall surfaces of the two tubes, said. tubes being longitudinally displaced for a short section of their length to provide correspondingly shortplug or socket coupling elements of equal length at the respective ends of the conduit, and

said conduit being impregnated throughout with awater-resistant material.

4. A prefabricated, double-walled fibrous conduit compri' two paper tubes secured together by a relatively thin film of adhesive, which is normally fluid at room temperatures and which adhesive is located on the contiguous wall surfaces of the two tubes, said tubes being of equal length and of very slightly different diameters such that one tube affords a relatively close slid-' ing fit inside of the other tube prior to bonding with said adhesive, the two tubes being longitudinally displaced for a short section of their length to provide correspondingly short plug or socket coupling elements of equal length at the respective ends of the conduit --and being impregnated with a thermoplasticwater-resistant material that renders the conduit durable and resistant to distintegratio'n when used underground. v

5. A fibrous conduit as defined in claim 2 and in which the plug or socket coupling elements are a proximately 1 to 3 inches in length.

6. A prefabricated, double-walled, fibrous conduit comprising two fibrous /tubes bonded togather, in fixed, concentric, telescoped relationship, by an adhesive that is in the form or a soft. easily spreadable paste at room temperatures and is deposited, as a relatively thin bonding film plug or socket coupling elements of equal length at the respective ends oi. the conduit, and said conduit being adapted for impregnation by a suitable waterproofing material. a

7. A prefabricated, double-walled, fibrous conduit comprising twofibrous tubes bonded together, in fixed, concentric telescoped'relationship, by a water soluble sodium silicate adhesive that is in the form of a soft, easily spreadable paste at room temperatures and is deposited as a relatively thin bonding film between'the contiguous walls of the two tubes, said tubes being displaced for a-short section of their length to provide correspondingly short plug or socket coupling elements of equal length at the respective ends of the conduit, and said conduit being adapted for impregnation by a suitable waterproofing material.

8. A prefabricated, double-walled, fibrous conduit comprising two fibrous tubes bonded to-.

gether, in fixed, concentric, telescoped relationship, by a water soluble dextrine adhesive that is in the form of a soft, easily spreadable paste at room temperatures and is deposited as a relatively thin bonding film between the contiguous walls of the two tubes, said tubes being displaced for a short section of their length to provide correspondingly short plug or socket coupling elements of equal length at thejespective ends of the conduit, and said conduit being adapted for impregnation by a suitable waterproofing, ma-,

of the coupling, and said coupling being adapted for impregnation by a suitable waterproofing material.

10.- A v prefabricated, double-walled, fibrous coupling comprising two relatively short fibrous tubes bonded together, in fixed, concentric, telescoped relationship, by an adhesive that is in the form of a soft, easily spreadable paste at room temperatures and is deposited as a relatively thin bonding film between the contiguous walls of the two tubes, said tubes being of unequal length and being located one within the other so as to provide relatively short plug elements of equal length at the respective ends of the coupling, and said coupling being adapted for impregnation by a suitable waterproofing material.

. at room temperatures and is deposited as a relatively thin bonding film between the contiguous walls of the two tubes, said tubes being displaced for a short section of their length to provide correspondingly short plug or socket coupling and adapter elements of equal length at the respective ends of the adapter-coupling, at least one end of the inner tube of said two concentric, telescoped tubes being tapered to provide an adapter element, said adapter-coupling being adapted for impregnation by a suitable water-' proofing-material.

12. A prefabricated, double-walled, fibrous adapter-coupling comprising two relatively short fibrous tubes of unequal length, bonded together, in'fixed, concentric, telescoped relationship, by an adhesive that is in the form of a soft, easily spreadable paste at room temperatures and is deposited as arelatively thin, bonding film between the contiguous walls of the two tubes. said tubes being displaced for a short section of their length to provide correspondingly short coupling elements of equal length at the respective ends of the adapter-coupling, at least one end of the inner tube of said two concentric, telescoped tubes being tapered to provide an adapter for coupling with a complementary shaped end of another conduit, and at least one end of said innertube being a plug end, and said adaptercoupling being 'adapted for impregnation by a suitable waterproofing material.

13. A prefabricated, double-walled, fibrous adapter-coupling comprising two relatively short fibrous tubes bonded together, in fixed, concentric, telescoped relationship, by an adhesive that is in the form of a soft, easily spreadable paste at room temperatures and is deposited as a relatively thin bonding film between the contiguous walls of the two tubes, said tubes being displaced for a short section of their length to provide correspondingly short plug or socket coupling elements of equal length at the respective ends of the adapter-coupling, the outer tube of this coupling having a relatively thick wall as compared with the inner tube which it surrounds, and at least one end of the inner tube being tapered to provide an adapter for coupling with another type of conduit, and said adapter-coupling being adapted for impregnation by a suitable waterproofing material.

' EDWARD S. REID. 

